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| United States Patent |
5,597,475
|
|
Kerr
, et al.
|
January 28, 1997
|
DADMAC/vinyl trialkoxysilane copolymers for dewatering copper and
taconite slurries in the mining industry
Abstract
A method for dewatering mineral slurries employing a copolymer of
diallyldimethlylammonium halide and a vinyl alkoxysilane, which is
preferably a copolymer of diallyldimethylammonium chloride and
vinyltrimethoxysilane as a coagulant is disclosed. The method for
dewatering mineral slurries containing water comprising the steps of:
feeding said mineral slurry into a thickener, treating said mineral slurry
with an effective amount of a coagulant which comprises a copolymer of
halide and a vinyl alkoxysilane; allowing the water to separate from the
mineral slurry, withdrawing the water from said thickener and discharging
said mineral products from said thickener. Mineral slurries which can be
effectively treated are copper and taconite. The above-mentioned method
may also include treatment with a flocculant in conjunction with the
coagulant.
| Inventors:
|
Kerr; E. Michael (Aurora, IL);
Ramesh; Manian (Lisle, IL)
|
| Assignee:
|
Nalco Chemical Company (Naperville, IL)
|
| Appl. No.:
|
508642 |
| Filed:
|
July 28, 1995 |
| Current U.S. Class: |
208/188; 44/620; 44/621; 208/187; 208/370; 210/734 |
| Intern'l Class: |
C10G 033/04; B01D 021/01; C10L 005/00 |
| Field of Search: |
208/188,187,370
210/734
44/620,621
|
References Cited
U.S. Patent Documents
| 3624019 | Nov., 1971 | Anderson et al. | 260/29.
|
| 4151202 | Apr., 1979 | Hunter et al. | 260/567.
|
| 4801388 | Jan., 1989 | Fong et al. | 210/701.
|
| 4929655 | May., 1990 | Tekeda et al. | 524/458.
|
| 5006590 | Apr., 1991 | Takeda et al. | 524/458.
|
| 5120797 | Jun., 1992 | Fong et al. | 525/329.
|
| 5296006 | Mar., 1994 | Reed et al. | 44/621.
|
| 5330546 | Jul., 1994 | Ramesh et al. | 44/620.
|
| 5476522 | Dec., 1995 | Kerr et al. | 44/626.
|
Primary Examiner: Caldarola; Glenn A.
Assistant Examiner: Hailey; Patricia L.
Attorney, Agent or Firm: Miller; Robert A., Drake; James J., Charlier; Patricia A.
Claims
What is claimed is:
1. A method for dewatering mineral slurries containing water wherein said
slurries are selected from the group consisting of copper and taconite
comprising the steps of:
a. feeding the mineral slurry into a thickener;
b. treating said mineral slurry with an effective amount of a coagulant
which comprises a copolymer of diallyldimethyl ammonium halide and a vinyl
alkoxysilane;
c. allowing the water to separate from the mineral slurry;
d. withdrawing water from said thickener; and
e. discharging the dewatered mineral products from said thickener.
2. The method of claim 1 wherein the diallyldimethylammonium halide is
diallyldimethylammonium chloride and the vinyl alkoxylsilane is vinyl
trimethoxysilane.
3. The method of claim 2 wherein the coagulant has a reduced specific
viscosity in one molar sodium nitrate solution for one percent polymer
actives from 0.2 to 5 dl/gm.
4. The method claim 2 wherein the coagulant has a reduced specific
viscosity in one molar sodium nitrate solution for one percent polymer
actives from 0.5 to 4.0 dl/gm.
5. The method of claim 2 wherein the coagulant has a reduced specific
viscosity in one molar sodium nitrate solution for one percent polymer
actives from 0.7 to 3.0 dl/gm.
6. The method of claim 2 wherein the mole ratio of diallyldimethyl ammonium
chloride to vinyl trimethoxysilane ranges from 99.99:0.01 to 80:20.
7. The method of claim 2 wherein the mole ratio of diallyldimethylammonium
chloride to vinyl trimethoxysilane ranges from 99.9:0.1 to 85:15.
8. The method of claim 2 wherein the mole ratio of diallyldimethylammonium
chloride to vinyl trimethoxysilane ranges from 99.9:0.10 to 95.0:5.0.
9. The method of claim 2 further comprising the addition of a flocculant to
said mineral slurries containing water.
10. The method of claim 9 wherein said flocculant is a copolymer of
acrylamide and acrylic acid.
Description
FIELD OF THE INVENTION
The present invention relates generally to the use of novel hydrophobically
associating polyelectrolyte compositions for dewatering mineral slurries.
These polyelectrolyte compositions are hydrophobically associating
copolymers of diallydimethylammonium halides, and particularly
diallydimethylammonium chloride (DADMAC) and vinyl alkoxysilaned,
preferably, vinyl trimethoxysilane (VTMS). The present application claims
priority from co-pending U.S. application Ser. No. 08/447,302 filed May
22, 1995, which is in turn a continuation-in-part U.S. application Ser.
No. 08/401,640 filed Mar. 8, 1995, the contents of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
Coal is the most abundant natural energy source in the world. A significant
portion of the U.S. dosmetic energy requirements are met by burning coal
as a fossil fuel. There are various types of coal found within the U.S.,
i.e., anthracite, semi-anthracite, low-volatile bituminous coal, medium
and high volatile bituminous coal, sub-bituminous coal, and lignite. Coals
such as anthracite and semi-anthracite typically have high ash and sulfur
contents and therefore require beneficiation prior to use.
The primary purpose of coal beneficiation is to reduce the incombustible
ash content, thus enhancing the heat content. Reduction in the ash content
results in savings in transportation and ash disposal costs. Sulfur,
mainly in the form of purite, is also reduced.
Another important economic factor to be considered in coal processing is
the recovery and reuse or process water. Water is typically very expensive
and there are often limits on total usage. Also, strict enviromental
controls prohibit or severely limit discharge of process water. Thus, it
is imperative that solids be efficiently removed from the process water
and water recycled to the process stream.
Beneficiation of coal is effected using two primary properties of coal,
i.e., ( 1) differences in specific gravity between coal and its
impurities, and (2) differences in surface characteristics between coal
and its impurities. Since the higher ash content fractions are usually
found in the finer coal sizes, some plants only screen out these sizes to
beneficiate the coal. However, since the quantity of such fine coal is on
the rise, even this is treated.
A coal beneficiation plant may be broadly divided into specific gravity
separation and fine coal treatment. In gravity separation, cleaning units
make use of the differences in specific gravity between coal and its
impurities to effect separation. Normally, the specific gravity of the
clean coal is less than that of its impurities. Some examples of commonly
used equipment for gravity separation are: jigs, heavy medium baths and
cyclones, washing tables, water-only cyclones and spirals.
Fine coal treatment incorporates a flotation cell(s), clean coal filter and
thickener. In the flotation cell, a collector and frother are added to the
flotation feed. A collector such as diesel oil selectively imparts
hydrophobicity to the coal particles. This increased hydrophobicity makes
the air bubbles more likely to attach to the coal particles. The frother,
generally an alcohol based product, reduces the surface tension of the
air/water interface, thus making a stable froth.
The clean coal concentrate from the flotation cells goes to the clean coal
filter and is dewatered. The tailings from the flotation cell go to the
thickener where they are thickened and discharged.
The thickener is treated with coagulants and flocculants to enhance
settling. Typically, the coagulants and flocculants are added at several
points along the feed line to the thickener and in different sequences.
Coagulation is the destabilization by surface charge neutralization of
stable negatively charged particles that are in suspension (i.e.,
settleable or dispersed) through the utilization of inorganic salts or
cationic polyelectrolytes. Flocculation is the aggregation of finely
divided particles which are suspended in a liquid through the utilization,
of an entrapping agent, generally an inorganic flocculant, or a bonding
agent, generally an organic flocculant, that brings the particles
together.
During the processing of coal, a coal refuse slurry is generated. This
slurry consists of residual coal fines and clays suspended in plant
process water. Due to the high volume of water used in the processing of
coal, it is necessary to reclaim the wash water for recirculation in the
plant. The concentrated solids are sent to an impoundment pond for
disposal. Generally, the use of anionic flocculants is sufficient to
remove the majority of the coal fines; however, when there are high levels
of clay in the mined coal, it is necessary to supplement the use of
anionic flocculants with the use of cationic coagulants. The sequential
addition of flocculants and coagulants is used primarily in the coal
refuse thickener and in the subsequent twin belt press filtration of the
thickener underflow. The typical application order in the thickener, which
is similar to a clarifier, is coagulant addition followed by flocculant
addition. This provides a controlled turbidity of the recycle process
water and a controlled solids settling rate. In the thickener underflow
filtration, the order of application is normally flocculant followed by
coagulant. This treatment gives highly agglomerated solids which provides
effective dewatering of the waste solids and low turbidity in the recycled
process water.
The decrease in sludge volume or the increase in sludge solids results in
more efficient use of plant process water and a reduced loading in the
impoundment pond. The impoundment pond is the area of the mine where the
sludge is used to landfill existing mined surfaces. With time, the sludge
further compresses in the impoundment area which provides reclaimed mine
sites.
The typical equipment used for sludge thickening and dewatering in the coal
industry are Gravity Thickener, Twin Belt Press, and Rotary Drum Filters.
Each of these pieces of equipment uses flocculants and coagulants. The
doses of flocculant and cationic polymers are 5-10 ppm and 1-5 ppm,
respectively, for the thickener and 5-20 ppm and 5-30 ppm, respectively,
for the filter applications. These polymers are highly surface active and
they remain with the solids that are sent to the impoundment pond. These
products are used in closed loop coal refuse treatment applications. A
treating polymer is also required for the dewatering of other mining
underflow solids such as copper ore refuse slurries.
In addition to the treatment of fine coals, dewatering is also necessary in
mineral processing. A variety of mineral slurries such as taconite,
copper, trona, sand and gravel slurries and titania require solids removal
and dewatering. The same basic processing steps are utilized to extract
titanium oxide from titania, for example.
Although some inorganics, principally alum and iron salts, are still used
as coagulants, water soluble organic polymers are now more prevalent. Both
naturally occurring and synthetic polymers find use as coagulants and
flocculants in the mining industry. The principal natural polymers used
are starch and guar, both of which are high-molecular weight polymers of
simple sugars, such as polysaccharides. Starch is a polymer of glucose
consisting of a mixture of linear (amylose) and branched segments
(amylopectin).
Synthetic polymers are advantageous because they can be tailored to a
specific application. This has resulted in a wide range of commercially
available coagulants and flocculants of varying charge, composition, and
molecular weight. The most widely used synthetic coagulants are
polydiallyldimethylammonium chloride (polyDADMAC) having molecular weights
in the range of from 100,000 to as high as 1,000,000 or higher and
condensation polymers of dimethylamine and epichlorohydrin (Epi/DMA) which
generally have molecular weights in the range of 20,000 to 100,000.
The present inventors have developed various novel hydrophobically modified
polyelectrolyte copolymers which may be used as coagulants in the
thickening process during mineral processing. These cationically charged
hydrophobically modified polymers which incorporate into the polymer
backbone a vinyl alkoxysilane, exhibit improved performance or activity in
thickening over conventional inorganic and organic coagulants. The unique
cationic and surface active polymers of this invention are advantageous
over conventional polymers because they are capable of both increased
surface activity, as evidenced by the lowering of surface tension, and
adsorption onto hydrophobic surfaces.
The advantages of the diallydimethylammonium chloride/vinyl trialkoxysilane
copolymers stem from the fact that they have the following
characteristics: 1) silicon components are capable of forming networks
with other silicon moieties, similar to crosslinking; and 2) incorporated
silicon functionalities are capable of adhering or adsorbing to
hydrophobic surfaces. The hydrophobically associating copolymers of the
instant invention demonstrate enhanced performance with replacement ratios
on the order of 0.35-0.50 over current commercially available poly
(DADMAC) treatments.
The present invention also provides many additional advantages which shall
become apparent as described below.
SUMMARY OF THE INVENTION
A method for dewatering mineral slurries employing a copolymer of
diallyldimethlylammonium halide and a vinyl alkoxysilane, which is
preferably a copolymer of diallyldimethylammonium chloride and
vinyltrimethoxysilane as a coagulant is disclosed. The method for
dewatering mineral slurries containing water comprising the steps of:
feeding said mineral slurry into a thickener, treating said mineral slurry
with an effective amount of a coagulant which comprises a copolymer of
halide and a vinyl alkoxysilane; allowing the water to separate from the
mineral slurry, withdrawing the water from said thickener and discharging
said mineral products from said thickener. Mineral slurries which can be
effectively treated are copper and taconite. The above-mentioned method
may also include treatment with a flocculant in conjunction with the
coagulant.
Other and further objects, advantages and features of the present invention
will be understood by reference to the following specification.
DESCRIPTION OF THE INVENTION
The present inventors have developed a new class of coagulants which
exhibit enhanced performance in dewatering of mineral slurries. These
coagulants are copolymers of DADMAC and trialkoxysilanes. Such
hydrophobically associating copolymers have an enhanced performance with
replacement ratios on the order of about 0.35 to about 0.50 over
commercially available poly(DADMAC) treatments.
The mineral slurries are preferably treated with coagulants and optionally
with flocculants. It has been discovered that surface charge
neutralization of colloidal particles in the mineral slurries can be
enhanced by the use of a copolymer which has been modified to incorporate
a certain degree of hydrophobicity. Such a modification can be
accomplished by copolymerizing a diallyldimethylammonium halide,
particularly diallyldimethylammonium chloride (DADMAC) with vinyl
alkoxysilane, preferably vinyl trimethoxysilane.
The vinyl alkoxysilane monomers useful in the copolymer composition of the
invention contain an alkyl group of from 1-4 carbon atoms. As such vinyl
trimethoxy, triethoxy, tripropoxy and tributoxysilanes, and combinations
thereof, may find use in the subject invention. While vinyl
trialkoxysilanes are preferred, the monomers may be mono or di-substituted
as well, or mixtures of mono-, di- and tri-alkoxy substituted silanes may
be used. A preferred vinyl trialkoxysilane for use in this invention is
vinyl trimethoxysilane, commercially available from Hals America,
Piscataway, N.J.
Diallyldimethylammonium halides, especially diallyldimethylammonium
chloride (DADMAC) are well-known and commercially available from a variety
of sources. One method for the preparation of DADMAC is detailed in U.S.
Patent No. 4,151,202, the disclosure of which is hereinafter incorporated
by reference into this specification.
The mole ratio of DADMAC to the vinyl trialkoxysilane ranges from 99.99:01
to 80:20 and, preferably from 99.9:0.1 to 85:15. Most preferably, the mole
ratio of DADMAC to the vinyl trialkoxysilane range from 99.9:0.1 to
95.0:5.0.
The polymers may be prepared as in conventional vinyl polymerization
techniques. These techniques include conventional solution polymerization
in water, and polymerization in water-in-oil emulsion form, such as that
described in U.S. Pat. No. 3,624,019, the disclosure of which is
hereinafter incorporated by reference into this specification. The
polymers of the invention may also be prepared in so-called dispersion
form, such as that described in U.S. Pat. Nos. 4,929,655 and 5,006,590 the
disclosures of which is also hereinafter incorporated by reference into
this specification. The polymers of the instant invention may be in solid,
dispersion, latex or solution form.
Conventional free radical catalysis may be used, including both free
radical initiators and redox systems. Such polymerizations are within the
purview of those skilled in the art and as such will not be elaborated on
in this specification.
The molecular weights of the copolymer prepared hereunder can vary greatly.
Generally, copolymers of diallyldimethylammonium chloride and vinyl
trimethoxysilane produced hereunder will have a molecular weight of from
50,000 to 5,000,000, and preferably 75,000 to 2,500,000, and most
preferably from 100,000 to 1,000,000. The polymers of this invention will
accordingly have a reduced specific viscosity for a one percent by weight
polymer solution as measured in one molar sodium nitrate of from 0.2-5
dl/gm and preferably from 0.5-4.0 dl/gm. A most preferred reduced specific
viscosity range is from 0.7-3.0 dl/gm. While discussed herein as
copolymers of diallyldimethylammonium halides and vinyl alkoxysilanes,
other monomers may be incorporated into the resultant polymers without
detracting from the spirit and intent of the invention. Possible monomers
that may be incorporated include, but are not limited to nonionic and
cationic vinyl monomers. These materials are exemplified by acrylamide,
and such cationic monomers as dimethylaminoethylmethacrylate and
dimethylaminoethyl acrylate and their respective water soluble quaternary
amine salts.
The copolymers of this invention may be used alone, or in combination with
a high molecular weight anionic or non-ionic water soluble or dispersible
flocculant. Such polymers include polyacrylamide, and copolymers of
acrylamide with acrylic acid and its water soluble alkali metal or
ammonium salts. As used herein, the term acrylic acid is meant to
encompass such water soluble salts. Also useful are such polymers as
sulfomethylated acrylamides as exemplified in U.S. Pat. Nos. 5,120,797 and
4,801,388, the disclosures of which are hereinafter incorporated by
reference into this specification. Other commercially available anionic
flocculant materials may also be utilized.
A preferred class of flocculants for use in this invention includes
copolymers of acrylamide and acrylic acid having a mole ratio of
acrylamide to acrylic acid of from 99:1 to 1:99 and preferably 99:1 to
50:50. Most preferably, the mole ratio of acrylamide to acrylic acid will
be 95:5 to 60:40. An especially preferred flocculant for use in this
invention has a mole ratio of acrylamide to acrylic acid of about 70:30.
The flocculants of this invention may be prepared in solution form, or in
water-in-oil emulsion form. The preparation of such flocculants is known
to those skilled in the art. The flocculants generally have molecular
weights ranging from as low as 1,000,000 to 20,000,000 or higher.
Preferred flocculants have a molecular weight of about 10,000,000. The
upper weight of molecular weight is not critical so long as the polymer is
water soluble or dispersible.
The flocculant is believed to cause the aggregation of the neutralized
colloidal particles which are suspended in the tailings suspension.
Aggregation is the result of either entrapping agents (i.e., inorganic
flocculants) or bonding agents (i.e., organic flocculants) bringing the
neutralized particles together.
The coagulants and flocculants can be added at several points along the
feed line to the thickener and in different sequences. The flocculants may
be added either prior to or subsequent to coagulant addition. A typical
thickener is a gravity sedimentation unit which is a cylindrical
continuous thickener with mechanical sludge raking arms. The tailings
(i.e., a solids/liquid dispersion) enter the thickener at the centerwell.
The coagulants and/or flocculants are added at points in the feed line
and/or centerwell. The number of addition points, sequence, flocculant,
coagulant, etc. are determined by laboratory cylinder tests for each
particular application. The flocculated solids settle to the bottom of the
thickener. The mechanical arms rake the sludge and it is discharged. The
clarified water overflows into a launder surrounding the upper part of the
thickener.
The copolymer of diallyldimethylammonium chloride and vinyl trialkoxysilane
is generally added to the thickener or mechanical filter device at a rate
of about 0.01 to about 0.3 lb/ton of slurry, and preferably 0.075 to about
0.25 lb/ton. Most preferably from about 0.1 to 0.25 lb of polymer is used
per ton of slurry. The amount of coagulant will vary according to the
particular stream to be dewatered. Flocculant may also be added to the
thickener in an effective amount, generally between about 0.01 to about
0.25 lb/ton of slurry.
After treatment of the slurry with sufficient coagulant and optional
flocculant, the thickener underflow or refuse (i.e., concentrated
tailings) are removed from the bottom of the thickener, while water and/or
other liquids are taken out overhead. The water can thereafter be recycled
as process water for use in the beneficiation process or disposed of in
impoundment ponds. The concentrated tailings or refuse from the thickener
can be thereafter disposed of, generally as landfill.
In most instances, adding a given amount of flocculant in two or more
increments results in better performance than adding the same amount of
flocculant in one increment. It is not unusual to be able to reduce the
amount of flocculant required by as much as 30-40% by multi-point addition
and still achieve the required settling rate. Multi-point addition may
also provide improved clarity (i.e., lower suspended solids) at a given
settling rate.
This practice is implemented in a beneficiation plant process by adding the
flocculant at different points in the feed line to the thickener. The
improvement results from reducing the amount of surface area that the
second or third portion of flocculant actually contacts when added to the
system, as well as improved distribution of the flocculant.
The present invention can best be understood by reference to the following
working and comparative examples.
EXAMPLE 1
A 90:10 mole copolymer of diallyldimethylammonium chloride (DADMAC) and
vinyl trimethoxysilane (VTMS), at 20% actives, was prepared for use as a
coagulant. The following reactants were used to form the hydrophobically
modified polyelectrolyte copolymer coagulant:
______________________________________
312.91 grams Diallydimethylammonium Chloride
DADMAC (a 58% Solution)
18.89 grams Vinyl Trimethoxysilane (a 98% Solution)
200.0 grams Deionized Water
1.80 grams [2,2'-Azobis (2-amidinopropane)]
Dihydrochloride Initiator
20.0 grams Sodium Chloride
446.20 Final Solution Water
0.1 grams Versene
______________________________________
A semi-batch process was used to prepare the DADMAC/VTMS copolymer.
A 1.5L reactor equipped with a mechanical stirrer a thermocouple, nitrogen
inlet/outlet tubes, condenser and two syringe pumps was set up. Vinyl
trimethoxysilane was taken in the first pump set at a delivery rate of 4.5
cc/hr. The second pump contained an aqueous solution of 2,2' azobis
(2-amidinopropane) dihydrochloride (1.2 g in 48.8 g DI water), and the
pump was set at 12.5 cc/hr.
The DADMAC, sodium chloride, and Versene were charged into a polymerization
reactor and heated to 52.degree. C. The reaction mixture was purged with
nitrogen. VTMS and initiator-containing pumps were started and the
polymerization was allowed to proceed.
A thick polymer started forming after about 2 hours. At the end of two and
a half hours, the viscosity increased to a point where continued agitation
was difficult. 200 ml of deionized water was then added. The reaction
continued for a period of 5 hours, and then subjected to a post treatment
at 82.degree. C. for 5 hours.
Product phase separated in two days and indicated extensive crosslinking as
shown below:
##STR1##
The phase-separated product swelled in water, yet was water-insoluble.
EXAMPLE 2
A 99.5/0.5 mole ratio copolymer of diallyldimethylammonium chloride
(DADMAC) and vinyl trimethoxysilane (VTMS), at 20% actives, was prepared
for use as a coagulant. The following reactants were used to form the
hydrophobic polyelectrolyte copolymer coagulant:
______________________________________
321.13 grams DADMAC (a 62% Solution)
1.00 grams VTMS (a 98% Solution)
0.2 grams Versene
258.8 grams Deionized Water
1.20 grams 2,2'-Azobis [2(2-imdazolin-2yl) propane
Dihydrochloride Initiator
61.00 grams Sodium Chloride
356.87 grams Dilution Water
______________________________________
A batch process was used to prepare the DADMAC/VTMS copolymer. A reactor
similar to the one described in Example 1 was used.
The DADMAC, VTMS, Versene, sodium chloride and deionized water were charged
into a polymerization reactor at a temperature of 58.degree. C.
Thereafter, the initiator (0.6 grams in 49.4 grams deionized water) was
charged into the reactor dropwise via a syringe pump at 12.5 cc/hour.
A thick polymer started forming after about 1.0 hour. At the end of 1.5
hours, the mixture was difficult to stir. At this point, deionized water
addition was started using a syringe pump set at 70 ml/hour. The reaction
continued for a period of 5.5 hours. After that, initiator (0.6 grams in
19.4 grams of deionized water) was added. The reactor was heated to
82.degree. C. and held at that temperature for 3 hours. The reaction
product was then diluted with 356.87 grams of water and stored. Reduced
specific viscosity and intrinsic viscosity measurements were determined on
a 1% polymer solution in NaNO.sub.3 (sodium nitrate) and found to be 2.02
and 1.3 dl/gm respectively.
EXAMPLE 3
A 99.0/1.0 mole ratio DADMAC/VTMS copolymer was prepared using the
procedure of Example 2. 2.0 g of VTMS and 355.07 g of DI water were used
in place of the amounts in Example II. All other quantities were the same.
RSV/IV for a 1% by weight solution of the polymer in sodium nitrate were
2.2 and 1.2 dl/g, respectively. This material is hereinafter referred to
as Example 3.
EXAMPLE 4
The gravity dewatering test is a tool for reliably screening products and
evaluating application variables for dewatering. Results obtained in
testing can generally be directly translated to the plant process. The
following procedure outlines suggested steps in performing a thorough test
program.
1. An apparatus consisting of a 500 ml graduated cylinder, powder funnel,
and plastic collar which retains a filter cloth on the top of the powder
funnel, all supported by a ringstand and appropriate clamps was
constructed. The filter cloth used was a nylon Filterlink.RTM. 400 mesh
round orifice cloth of a type similar to that used in commercial practice.
2. Obtain 5-10 gallons of untreated dewatered feed (clarifier underflow).
3. Using a spatula, hand mix the slurry to uniformly disperse any coarse
solids present. Immediately sample and transfer 200 ml of underflow slurry
into a 500 ml graduated cylinder. Re-mix the underflow slurry prior to
filling each new cylinder.
4. Measure in a syringe and set aside the desired amount of coagulant as 1%
solutions. Measure and add the desired amount of anionic polymer
flocculant stock solution to a 50 or 100 ml graduated cylinder, dilute to
a total of 20 ml (or 10% of the underflow slurry volume) with process
water, mix thoroughly, and set aside.
5. Invert the 500 ml graduate cylinder containing the 200 ml of underflow
slurry 4 times to thoroughly disperse the solids, then immediately add the
pre-measured flocculant solution from step 3, re-stopper the cylinder and
invert 4 times. Duplicate the mixing motion as closely as possible in each
test.
6. Immediately add the pre-measured coagulant solution, re-stopper and
invert 2 additional times.
7. Pour the conditioned slurry into the plastic collar section of the test
apparatus and immediately start a stopwatch. Record the drainage volumes
collected every 10 seconds for a time period greater than actual
commercial plant process time for gravity drainage. After removing the
plastic collar, note the dewatered cake stability and thickness. If the
thickness is significantly different from plant conditions, adjust the
initial test slurry volume in step 2 accordingly.
8. Repeat testing, adjusting products and dosages to obtain maximum free
drainage volumes in the process time allowed.
Turbidity was measured with a Hach ratio/xR turbidimeter. The results of
the testing performed at a midwestern mine are tabulated below in Table I.
The blank is included for comparison purposes to demonstrate that the
turbidity of the untreated mineral slurry is very high. The settling rate
results indicate comparable settling may be achieved by polymers of the
instant invention to settling rates achieved with conventional
poly(DADMAC) treatment. However, the polymers of the instant invention are
much more active, as demonstrated by lower dosages utilized.
TABLE I
__________________________________________________________________________
Taconite Field Trial Results
Cationic Flocculant
Dosage Dosage
(mls of 0.1% (mls of 0.1%
Turbidity
Settling Rate
Cationic Polymer
sol'n.)
Flocculant
sol'n.)
(NTU)
(inches/min)
__________________________________________________________________________
None 0.00 poly 0.45 439 8.8
(AcAm/AA).sup.2
latex 0.20 poly 0.45 173 15.0
poly(DADMAC) (AcAm/AA).sup.2
0.20 0.45 197 13.3
0.20 0.22 246 7.6
0.10 0.22 392 7.6
0.06 0.15 460 5.0
0.06 0.15 504 4.1
0.06 0.10 618 4.5
Example 3.sup.3
0.03 poly 0.15 778 3.8
(AcAm/AA).sup.2
0.04 0.15 628 4.9
0.04 0.10 530 3.9
0.06 0.05 411 4.4
poly(DADMAC).sup.1
0.8 496 3.3
2 241 4.7
BLANK 1832 0.8
__________________________________________________________________________
.sup.1 = commercially available dry polymer of polydiallyldimethylammoniu
chloride having approximately the same intrinsic viscosity as polymer of
Example 3. Product is commercially available from Nalco Chemical Company,
Naperville, Illinois.
.sup.2 = the anionic poly(AcAm/AA) with a 70:30 molar ratio of acrylamide
to acrylic acid.
.sup.3 = 99:1 mole ratio of poly(DADMAC/VTMS) synthesized according to th
procedure of Example 3.
EXAMPLE 5
A standard filter test leaf procedure which generates a filter cake whose
weight and thickness thereafter are determined was utilized at a
southwestern mining facility to obtain the results of Table II. The slurry
sample size in each test was 600 mls of mineral slurry with a 30 second
form time and a 90 second drying time.
The results indicate that the polymer of the instant invention works as
well as conventional poly(DADMAC) treatments, yet at much lower
concentrations.
TABLE H
__________________________________________________________________________
Copper Processing Field Trial Results
Lb/Ton latex
Lb/Ton Lb/Ton Increase
poly(DADMAC)
Example 3.sup.1
poly(DADMAC).sup.2 % Yield
% Yield
40% polymer
20% polymer
40% polymer
Wet
Dry
% Weight
#/sq.
vs. Poly
Sample
actives actives
actives Wt.
Wt.
Moisture
Changes
ft (DADMAC).sup.2
__________________________________________________________________________
#1 0 0 0 114.1
98.4
13.8 -- 2.17
--
#2 0 0 1 82.6
72.2
12.8 <20.0%>
1.59
--
#3 0.25 0 0 177.7
153.7
13.5 50% 3.39
113.0%
#4 0.5 0 0 252.7
220
12.0 124% 4.85
205.00%
#5 0.75 0 0 288.7
251.6
12.8 156% 5.55
249%
#6 0 0.25 0 137.7
118.4
14 21 2.61
64%
#7 0 0.5 0 176.7
153.7
12.9 56% 3.39
113.00%
#8 0 0.75 0 246.7
216
12.4 120 4.76
199%
__________________________________________________________________________
.sup.1 = 99:1 mole ratio of poly(DADMAC/VTMS) synthesized according to th
procedure of Example 3.
.sup.2 = commercially available dry polymer of polydiallyldimethylammoniu
chloride having approximately the same intrinsic viscosity as polymer of
Example 3. Product is commercially available from Nalco Chemical Company,
Naperville, Illinois.
While we have shown and described several embodiments in accordance with
our invention, it is to be clearly understood that the same are
susceptible to numerous changes apparent to one skilled in the art.
Therefore, we do not wish to be limited to the details shown and described
but intend to show all changes and modifications which come within the
scope of the appended claims.
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